<?php
	/**
	 * Expression
	 * Represents an expression used in select/update/insert/delete statements
	 * 
	 *  Examples (expressions are inside double square brackets):
	 *  	select [[columnA]], [[columnB as aliasB]] from tableA
	 *  	update tableA set [[columnA = valueA]] where columnB = something
	 *
	 * @author Corina
	 * @package /classes/db/queryparts/expression
	 * @version 0.1
	 */
	class Expression {
		/**
		 * column name
		 * @var string
		 */
		var $column_name;
		
		/**
		 * constructor
		 * @param string $column_name
		 * @return void
		 */
		function Expression($column_name){
			$this->column_name = $column_name;
		}
		
		function getColumnName(){
			return $this->column_name;
		}
		
		function show() {
			return false;
		}
		
		/**
		 * Return column expression, ex) column as alias
		 * @return string
		 */
		function getExpression() {
		}
	}
